1. Technical Field
The present invention relates generally to switches in a packet switched network, and more specifically, to address lookup tables for locating information relating to packets in a packet switched network.
2. Background Art
In computer networks, a plurality of network stations are interconnected via a communications medium. For example, Ethernet is a commonly used local area network scheme in which multiple stations are connected to a single shared serial data path. These stations often communicate with a switch located between the shared data path and the stations connected to that path. Typically, the switch controls the communication of data packets on the network.
The network switch includes switching logic for receiving and forwarding frames of information to the appropriate destinations. One arrangement for generating a frame forwarding decision uses a direct addressing scheme, where the network switch includes an address table storing switching information for the destination addresses.
For example, a frame may be received by the network switch with header information indicating the source address and destination address of the frame. The switching logic accesses the address table using the source address and destination address as lookups to find the appropriate frame forwarding information. The switch then uses this information to send the frame to the appropriate destination.
When all of the stations connected to the network are simultaneously operating, packet traffic on the shared serial path can be heavy with little time between packets. Accordingly, it is desirable to look up the frame forwarding information in the address lookup table as quickly as possible. By increasing the size of the lookup table, more information can be stored, thus increasing the chances that the frame forwarding information will be found in the lookup table, and thus potentially decreasing the average time to determine the frame forwarding information. Increasing the size of the lookup table, however, also has the undesirable property of increasing the average time to perform each lookup.
Thus, there is a need in the art to improve the functionality of the lookup table in network switches, such as an Ethernet switch.